The purpose of this thesis is to design an organisation attempting to facilitate cross-sectoral, action-oriented collaboration to influence systemic change towards sustainability, and to create a Design Guide for achieving this objective. To answer this, we conducted a participatory action research with Smart Urbanism: London (SU:LDN) as a case study. This is a start-up organisation whose goal is to introduce the paradigm of complexity thinking to the planning, design and delivery of cities in order to create a new, responsive and sustainable urban fabric. They intend to faciitate a mass collaboration across the relevant sectors. The Framework for Strategic Sustainable Development (FSSD) was used as a lens for the overall research, the analysis of SU:LDN and the construction of the Design Guide.